Build a smooth low poly foot stool with lower than 15K Tris / Faces
As suggested by Rob, use Normals. Also, your material will count to fake the texture (put a bit of noise and glossy in it) but it's not the topic here.


Create a low-poly object, give it a Subdivision Surface modifier and Smooth Shade it.





You could duplicate your object to sculpt a high-poly version, but an even simpler technic is to keep one object and to fake the high-poly version with the Multires modifier. So give your object a Multires modifier and click Subdivide several times (5 times here).





In Sculpt mode, begin to sculpt all your wrinkles and details.





In the UV/Image Editor, create a new black image. Unwrap your object with the Smart UV Project mode. Create a material with an Image Texture, load the previously created image, but for the moment don't plug the Image Texture into the Diffuse. Go in the Properties panel > Render > Bake, Bake Type > Normal, click on the Bake button, the normal map will appear on the UV/Image Editor.





Now duplicate your object with its modifier and keep a copy somewhere. Delete the Multires modifier on the original. Plug the Image Texture (Non-Color Data mode) into a Normal Map, plug it into the Normal socket of the Diffuse. Boom the wrinkles appear on your object as if they were in 3D.